Forward-wave enhanced radiation in the terahertz electron cyclotron maser

Based on the principle of electron cyclotron maser(ECM),gyrotrons are among the most promising devices to generate powerful coherent terahertz(THz)radiation and play a vital role in numerous advanced THz applications.Unfortunately,THz ECM systems using a conventional high-Q cavity were theoretically and experimentally demonstrated to suffer from strong ohmic losses,and,accordingly,the wave output efficiency was significantly reduced.A scheme to alleviate such a challenging problem is systematically investigated in this paper.The traveling-wave operation concept is employed in a 1-THz third harmonic gyrotron oscillator,which strengthens electron-wave interaction efficiency and reduces the ohmic dissipation,simultaneously.A lossy belt is added in the interaction circuit to stably constitute the traveling-wave interaction,and a down-tapered magnetic field is employed to further amplify the forward-wave(FW)component.The results demonstrate that the proportion of ohmic losses is nearly halved,and output efficiency is nearly doubled,which is promising for further advancement of high-power continuous-wave operation of the ECM-based devices.

Proteomics analysis on hypolipidemic mechanisms of total phenylpropanoid glycosides from Ligustrum robustum(Roxb.) Blume in hamsters fed a high fat diet

OBJECTIVE To explore the hypolipidemic mechanisms of the total phenylpropanoid glycosides fromLigustrum robustum(Roxb.) Blume(LRTPG) in hamsters using proteomics technique.METHODS The hamsters were fed with a high fat diet to induce hyperlipidemia.Then LRTPG of high(1.2 g·kg^(-1)),medium(0.6 g·kg^(-1)) and low(0.3 g·kg^(-1)) doses were administrated daily for 4 weeks.Then the concentrations of plasma and hepatic lipids were determined using enzymic methods.The total protein was extracted from livers of the model group and the group treated with the high dose of LRTPG for label-free quantitative proteomics.RESULTS LRTPG significantly reduced the concentrations of plasma and hepatic lipids in hamsters fed a high fat diet.The proteomics data showed that a total of 2231 proteins were identified,and 549 proteins were found to be differentially expressed between the model group and the group treated with LRTPG.Among the 549 proteins,93 proteins were up-regulated and 59 proteins were down-regulated,and 397 proteins were absent or not.And some of these proteins were much related to the lipid metabolism.Further,gene ontology(GO) analysis indicated metabolic process,transport,oxidation-reduction process,phosphorylation,signal transduction,lipid metabolic process were the main biological processes that those differentially expressed proteins participated.KEGG pathway analysis showed that those proteins were involved in several metabolic pathways including oxidative phosphorylation,non-alcoholic fatty liver disease(NAFLD),PI3K-Akt signaling pathway,cAMP signaling pathway,cGMP-PKG signaling pathway.CONCLUSION The proteomics study could provide valuable clues to help us to understand the hypolipidemic mechanisms of LRTPG much better.

Plasmonic vortex beam emitter

Terahertz vortices prompt numerous advanced applications spanning classical and quantum communications,sensing, and chirality-based detection, owing to the inherent physical properties of terahertz waves and orbital angular momentum(OAM). Nonetheless, existing methodologies for generating terahertz vortices face challenges such as unalterable topological charges and intricate feed networks. To address these limitations, we propose a novel approach to generate multi-mode and tunable vortex beams based on chiral plasmons. Through eigenmode analysis, the uniform helical gratings are demonstrated to support chiral plasmons carrying OAM. By leveraging their vortex characteristics and introducing modulation into the periodic system, these chiral plasmons are alternatively diffracted into high-purity vortex radiations according to the Bragg law. To validate the theory, the vortex beam emitter is fabricated and measured in the microwave regime based on the modulated scheme. Experimental results confirm the emission of vortex beams with desirable phase distributions and radiation patterns. Our findings highlight the potential of chiral plasmons as seeds for tunable and compact vortex radiation, offering promising applications in tunable vortex sources.

Broadband infinite-Q plasmons enable intense Smith–Purcell radiation

With the rapid development of nanophotonics for enhancing free-electron radiation,bound states in the continuum(BICs)have emerged as a promising approach for emitting intense Smith–Purcell radiation(SPR)with enhanced intensity.However,current BIC-based methods are limited to single-frequency operation,thereby restricting their applications requiring spectral and angular tunability,such as particle detectors and light sources.To overcome this limitation,this work proposes an approach for constructing plasmonic BICs over a broad spectral range in symmetry-broken systems.By leveraging the high-Q resonances near the BICs,we achieve intense SPR with broadband tunability,potentially improving the radiation intensity by six orders compared to traditional methods.Experimentally,we validate the construction of BIC using plasmonic antennas and achieve broadband demonstration.Our proposed concept can be extended to other plasmonic or guided-wave systems,paving the way toward compact and efficient free-electron sources in hard-to-reach frequency regimes.